Base material for synthetic leather, and apparatus for the production thereof

ABSTRACT

An apparatus for producing a dense stitched fleece includes a treatment chamber, one or more sieve drums rotatably disposed in said treatment chamber for conveying a fleece therethrough, inlet means for introducing the fleece to the treatment chamber, fan means associated with the sieve drum means for subjecting the interior of the sieve drum means to a suction draft and for drawing a treatment medium therethrough, heating means disposed in a circulation zone of the treatment chamber for heating the treatment medium, perforated felt means associated with at least a portion of the surface of the sieve drum means for compressing the fleece held on a sieve drum means by said suction draft, and outlet means for removing the compressed stitched fleece from the treatment chamber, at least a part of the perforated belt means being positioned in the proximity of said outlet means.

United States Patent 1191 1111 3,912,432 Fleissner Oct. 14, 1975 [54] BASE MATERIAL FOR SYNTHETIC 2,803,577 8/1957 Colt et a1. 425 373 x LEATPIER AND APPARATUS FOR TIJE 2,812,542 11/1957 Bleher 425/373 X 3,039,137 6/1962 Smith et a]... 425/373 X PRODUCTION THEREOF 3,515,609 6/ 1970 Rudloff 264/1 13 X [75] Inventor: Heinz Fleissner, Egelsbach,

Germany Primary ExaminerRobert L. Spicer, Jr. [73] Assigneez p AG, Switzerland Attorney, Agent, or FzrmCra1g & Antonelli 22 Filed: Aug. 12, 1974 57 ABSTRACT [2]] Appl. No.: 496,896 An apparatus for producing a dense stitched fleece includes a treatment chamber, one or more sieve drums Related Apphcatlon Data rotatably disposed in said treatment chamber for con- [62] Division of Ser. No. 14,808, Feb. 17, 1970, Pat. No. veying a fleece therethrough, inlet means for introduc- 3,876,745- ing the fleece to the treatment chamber, fan means associated with the sieve drum means for subjecting the Foreign pp q y Dam interior of the sieve drum means to a suction draft and Feb. 17, 1969 Germany 1907860 for drawing a treatment medium therethrough, heating means disposed in a circulation zone of the treatment [52] US. Cl. 425/75; 264/122; 425/83; chamber for heating the treatment medium, perfo- 425/373; 425/384 rated felt means associated with at least a portion of [51] Int. Cl. B29C 15/00 the surface of the sieve drum means for compressing [58] Field of Search 425/75, 80, 373, 83, 73, the fleece held on a sieve drum means by said suction 425/384; 264/113, 122, 92 draft, and outlet means for removing the compressed stitched fleece from the treatment chamber, at least a [56] References Cited part of the perforated belt means being positioned in UNITED STATES PATENTS the proximity of said outlet means.

2,776,452 l/1957 Chavannes 425/373 X 7 Claims, 2 Drawing Figures BASE MATERIAL FOR SYNTHETIC LEATHER, AND APPARATUS FOR THE PRODUCTION THEREOF This is a division of application Ser. No. 14,808 filed Feb. 17, l970, now U.S. Pat. No. 3,876,745.

BACKGROUND OF THE INVENTION The present invention relates to a base material (substrate) for synthetic leather, and to a process-and apparatus for the production of a densely stitched fleece comprising at least two types of fibers, one of which is employed as the binding fiber. This fleece, which is suitable as a base material for synthetic leather, can be strengthened by means of a thermal treatment.

It is conventional to utilize stitched fleeces as a base material for synthetic leather. These fleeces generally contain a large proportion of high-shrinkage fibers, for example about 30-50%, or more. In case highshrinkage fibers of polyesters or polyamides are employed, the shrinking step is most advantageous conducted in a water bath heated to a temperature of about 9095C. However, in this connection, considerable difficulties are encountered in obtaining a uniform shrinkage over a specific width of the material. A uniform shrinkage is necessary since this produces the closeness (denseness) in the material. Only when the density is uniform is it possible to obtain uniform properties in synthetic leather. When using polypropylene as the shrinkage fiber, the shrinkage is carried out in heated air. By means of the shrinking process, a very close, dense and compact fleece is obtained exhibiting a correspondingly good fluxural elasticity. Because of the difficulty encountered in obtaining a uniform shrinkage, it is also known to employ knitted and woven fabrics as the base. These fabrics are expensive in their manufacture, and the final products do not possess properties equal to a synthetic leather utilizing a shrunk fleece as a base material. In order to avoid the difficult shrinking process, it has also been suggested to use a stitched fleece as a base (carrier or substrate) material, said fleece having a certain proportion of binding fibers. These fleeces are very voluminous and do not exhibit the closeness of a shrunk fleece and thus do not exhibit the good properties of a shrunk fleece.

SUMMARY OF THE INVENTION An object of the present invention is to avoid the prior art disadvantages in providing a base material for synthetic leather.

Another object of the present invention is to provide an improved process'and apparatus for producing a base material for synthetic leather wherein a good bonding of the individual fibers and a uniform compactness of the fibers is achieved. I

A further object of the present invention is the difficulties encountered in the treatment of shrunk fleece but, at the same time, imparting to the base material the similar advantageous properties of a shrunk fleece.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it would be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications with the to avoid spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Pursuant to the present invention, it has been found that the above-mentioned disadvantages may be eliminated and a much improved process and apparatus for producing a base material for synthetic leather may be obtained by heating the stitched fleece to the melting or softening temperature of the binding fiber, compressing the fleece, and then cooling the fleece during the compression step. The compression (pressing) step effects, on the one hand, a very good bonding of the individual fibers to one another by welding, and, on the other hand, a considerable compacting of the fleece. By cooling the fleece during the pressing step, the fleece is simultaneously solidified in the compressed condition, so that as a result thereby a very close fleece is produced which, additionally, is also extremely uniform, particularly in its closeness (compactness).

It is advantageous to conduct the heating process utilizing air, steam, or a steam-air mixture as the treatment medium, wherein this treatment medium is drawn through the fleece. In order to compress the fleece, at least one pair of cooled rolls can be employed, and for cooling purposes, air can be utilized.

It is furthermore advantageous to hold the fleece compressed between two screens, at least during the cooling step, and to guide it therebetween, with a gaseous or liquid cooling medium, e.g., air, steam, or water, being conducted through the fleece during the cooling process. The feature of starting the compression of the fleece while it is in the plastic condition of the melt fiber afford the advantage that a more satisfactory welding is achieved due to the relative movement of the individual fibers with respect to one another. A particularly good fleece for a base material for synthetic leather is obtained according to the present process by providing that the fleece contains up to about 50% binding fibers, preferably about 10-15% of said melt fibers or binding fibers, and is strengthened by a thermal treatment and a pressure treatment as described above. By increasing the proportion of binding fibers, the closeness of the fleece can be enhanced.

A fleece consists of a specific fiber having a specific melting point. If another fiber'having a different chemical composition and a lower melting point is added to this fiber, it serves as a binding fiber when the temperature of the fleece is increased in the range of the melting point of said another fiber. Thus, the fleece as defined by the present invention comprises at least two of any material of synthetic fibers having a defined melting point, at least one of said fibers having a melting point lower than that of the remaining fibers.

The fibers which can be utilized by the present inven- "tion include any of the natural or synthetic fibers. The

natural fibers can include cotton, wool, silk, cellulose, etc., and the synthetic fibers may comprise synthetic polymers such as polyolefins, e.g., polyethylene, polypropoylene, etc., polyamides, e.g., Nylon 6 obtained by condensation of caprolactam, Nylon 66 obtained by the condensation of hexamethylenediamine with adipic acid, etc., polyesters, e.g., polyethylene terephthalate, etc., phenolic resins, e.g., phenol formaldehyde resins, urea formaldehyde resins, etc., polyvinyl materials, e.g., polyvinyl chloride, polyvinyl acetate etc., and acrylate resins, such a polymethylmethacrylate. Copolymers of these materials with one another or with ethylenically unsaturated monomers, and similar type polymers are also encompassed by the present invention. Typical fleece compositions include, for example, polyester fibers utilizing polypropylene or polyamides as the binding fiber.

A good, uniform coalescence and thus a fleece which possesses an extraordinary uniform strength is obtained by combining the two types of fibers to a bi-component fiber. Such a fleece can also be advantageously produced as a spun fleece from endless fibers. A fleece of this type exhibits an especially high fluxural elasticity and a wrinkle-recovery angle of about l70-I 80C. Examples of bicomponent fibers include Nylon 66 and Nylon 6, Orlon 21, 23 and 27 a polyester with a polyamide, and H81 and Nylon.

For the manufacture of such fleeces, it is suggested to employ an apparatus containing at least one sieve drum subjected to a suction draft, for heating the binding fibers to the melting temperature. Also, a perforated belt which is associated with the sieve drum is provided in the proximity of the outlet of the treatment chamber, said belt applying an initial pressure against the sieve drum and the fleece disposed thereon. It is also advantageous to draw in by suction fresh air for cooling the fleece, at least in a portion of this zone.

It is also possible, in the case of certain fleeces, to provide after the sieve drum at least one pair of cooled compression rolls, in a place of such a performated belt. A cooled pair of compression rolls can be advantageously employed when treating thin fleeces wherein the cooling is extensively effected by contact with the compression rolls. In the case of thick fleeces, an apparatus with the above-described perforated belt is more desirable.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only and thus are not limitative of the present invention and wherein FIG. 1 shows a longitudinal section through the apparatus;

FIG. 2 shows a cross-section through the apparatus of FIG. 1 along line A-A of FIG. 1.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, the apparatus of the present invention comprises a heat-insulated housing 1, containing a sieve drum 2, subjected to a suction draft. Above and beneath the sieve drum 2, heating elements 3 are provided for heating the circulated treatment medium, for example air and/or steam. At the front face thereof, the sieve drum is provided with a fan 4, which drawn the treatment medium out of the sieve drum and blows it back to the outer surfaceof said sieve drum, by way of additional heating elements 5. In the sieve drum 2, a cover plate 6 is arranged at that side of the sieve drum, which is free from the material being treated. The cover plate prevents the treatment medium from entering the sieve drum at this side. The fleece 7 to be strengthened is fed to the sieve drum 2 on a conveyor belt 8, in the apparatus shown in the drawings, and is suddenly heated, in a shock-like manner, to the treatment temperature, by drawing the treatment medium into the first drum through the fleece disposed on the sieve drum. A perforated belt 9 is associated with a portion ofthe periphery ofthe sieve drum, said belt, which is under tension or pressure, functioning to compress the fleece. By utilizing this compressing step, a more satisfactory welding together of the binding fibers with the other fibers is accomplished. At the same time, the fleece is prevented from lateral shrinking by means of the bilateral guidance. This is particularly important when polypropylene is employed as the binding or shrinking fiber. In the proximity of the outlet of the apparatus, fresh air is drawn into the treatment chamber through an opening 10. This fresh air cools the fleece compressed between the perforated belt 9 and the sieve drum 2, and thus the fleece structure is solidified in the compressed state. In place of cooling by means of fresh air, it is also possible to effect the cooling by a pair of cooled compression rolls l1 arrangedat the outlet of the apparatus. However, this pair of compression rolls 11 can also be additionally provided. The fan drive 12 and the drum 13 are attached at the outside of the housing 1.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be apparent to one skilled in the art are intended to be included.

What is claimed is:

1. An apparatus for producing a dense stitched fleece which comprises a treatment chamber, at least one sieve drum means rotatably disposed in said treatment chamber for conveying the fleece therethrough, inlet means for introducing the fleece to be treated to the treatment chamber, fan means associated with the sieve drum means for subjecting the interior of said sieve drum means to a suction draft, heating means disposed in the circulation zone of the treatment chamber, pretensioned sieve means associated with at least a portion of the surface of the sieve drum means and in the proximity of the outlet to the treatment chamber for compressing the fleece therebetween, drive means for driving the fan means, drive means for rotating the sieve drum means and outlet means for removing the dense stitched fleece from the treatment chamber.

2. The apparatus of claim 1, wherein the sieve means is a perforated belt means.

3. The apparatus of claim 2, wherein the outlet means includes an aperture provided in the treatment chamber, said perforated belt means extending out of the treatment chamber through said aperture.

4. The apparatus of claim 3, wherein a plate means is hinge-mounted to the treatment chamber at the outlet aperture, said plate means being adapted to cover and expose that portion of the perforated belt means extending through said aperture.

5. The apparatus of claim 4, whereina pair of cooled compression rolls are provided behind the aperture outlet of the treatment chamber.

6. The apparatus of claim 1, wherein said outlet means includes an outlet aperture for discharge of said fleece and a pair of cooled compressioned rolls are provided adjacent to the outlet aperture of the treatment chamber.

7. The apparatus of claim 1, wherein said outlet means includes an outlet aperture provided in said treatment chamber, and further comprising means in the proximity of said outlet aperture for allowing fresh air to be drawn into said treatment chamber by said vsuction draft whereby saidfresh air cools the fleece compressed between the sieve means and the sieve drum means. 

1. An apparatus for producing a dense stitched fleece which comprises a treatment chamber, at least one sieve drum means rotatably disposed in said treatment chamber for conveying the fleece therethrough, inlet means for introducing the fleece to be treated to the treatment chamber, fan means associated with the sieve drum means for subjecting the interior of said sieve drum means to a suction draft, heating means disposed in the circulation zone of the treatment chamber, pretensioned sieve means associated with at least a portion of the surface of the sieve drum means and in the proximity of the outlet to the treatment chamber for compressing the fleece therebetween, drive means for driving the fan means, drive means for rotating the sieve drum means and outlet means for removing the dense stitched fleece from the treatment chamber.
 2. The apparatus of claim 1, wherein the sieve means is a perforated belt means.
 3. The apparatus of claim 2, wherein the outlet means includes an aperture provided in the treatment chamber, said perforated belt means extending out of the treatment chamber through said aperture.
 4. The apparatus of claim 3, wherein a plate means is hinge-mounted to the treatment chamber at the outlet aperture, said plate means being adapted to cover and expose that portion of the perforated belt means extending through said aperture.
 5. The apparatus of claim 4, wherein a pair of cooled compression rolls are provided behind the aperture outlet of the treatment chamber.
 6. The apparatus of claim 1, wherein said outlet means includes an outlet aperture for discharge of said fleece and a pair of cooled compressioned rolls are provided adjacent to the outlet aperture of the treatment chamber.
 7. The apparatus of claim 1, wherein said outlet means includes an outlet aperture provided in said treatment chamber, and further comprising means in the proximity of said outlet aperture for allowing fresh air to be drawn into said treatment chamber by said suction draft whereby said fresh air cools the fleece compressed between the sieve means and the sieve drum means. 